Relatively little is known about the origins, types, quantities, and infectivities of viruses that occur in foods. The relationships between the amounts and kinds of bacterial and viral contamination and the roles that viruses play in food poisoning also are relatively obscure. The present studies are aimed at obtaining a better definition of the problem(s) that exist in relation to viruses in foods. We plan to measure the viral "loads" of specific market foods, such as hamburger. We will use techniques that have appeared in the literature and new methods that we will develop. One of the new methods involves immuno-adsorption of the viruses from food homogenates onto the walls of plastic tubes and surfaces of glass beads. After the viruses have been removed from the foodstuffs, the antigen-antibody complexes will be disrupted to release the viruses and the viruses will be concentrated and sedimented onto electron microscope grids for staining and observation. Similar samples will be concentrated for inoculation into tissue cultures (controls). Since the greatest problem is that of virus concentration, most effort will be directed toward the use of immuno-adsorbants (which have not been used before for such purposes) as well as conventional adsorbants (such as PEP-60 and talc) for isolation of the virus particles. The polioviruses will be used as the test system; we have already learned that the MS2 bacteriophage of Escherichia coli is not sufficiently representative of the enteroviruses to be suitable. One goal is to determine whether or not conventional methods recover most of the viruses present in foods; direct visualization might help to answer this question. Once methods have been developed for the polioviruses, the methods will be applied to the direction of other enteric viruses and, possibly, non-related vertebrate viruses. Estimates also will be made of the numbers of fecal coliforms and enterococci in the food samples, to discover if any relationships exist between virus content and indicators of fecal pollution.